The present invention relates to a polishing apparatus, in particular, a semiconductor wafer polishing apparatus.
A typical semiconductor wafer polishing apparatus includes, as shown in FIG. 6, a polishing pad 3 provided on an upper surface of a turn table (not shown), a wafer carrier 2 for carrying a wafer 1 to be polished and a shaft-like support 4 connected to the carrier 2 at the lower end thereof through a universal joint 5. The support 4 is adapted to be drivingly rotated around its axis by means of a motor (not shown) connected to the support and the universal joint 5 is adapted to transmit a rotational torque from the support to the carrier 2 to rotate the carrier about its axis while allowing the carrier 2 to pivot about the universal joint 5.
In operation, the turn table with the polishing pad 3 is drivingly rotated and the support 4 is positioned so that the wafer 1 carried by carrier 2 is brought into contact with a flat polishing surface 3' of the polishing pad 3 with a degree of pressure F, with the support 4 being simultaneously drivingly rotated, whereby the surface of the wafer 1 contacting the polishing surface of the polishing pad is polished.
Accordingly, a friction force f between the polishing pad and the wafer causes an angular moment M which acts on the carrier 2 with the wafer 1 about the universal joint 5 or the connecting point between the carrier 2 and the support 4, whereby the carrier with the wafer tilts about the universal joint 5 thereby causing an unevenness or gradient in a pressure generated between the contacting surfaces of the wafer and the polishing pad. This causes a deterioration in quality of the polishing operation.